Method of manufacturing a rolling element bearing provided with a cage

Abstract: The invention relates to a method of manufacturing a cage from a thermoplastic polymer-containing material for a roller bearing and a method of manufacturing a roller bearing comprising such a cage. By cross-linking the polymeric material its properties, such as form retention and compatibility with lubricants, are improved. A roller bearing provided with a cage made from suitably cross-linked thermoplastic polymer-containing material can be used even at temperatures above the melting point of the polymer. According to the invention a roller bearing is manufactured by forming a cage from thermoplastic polymer-containing material, providing it with rotating bodies and only then cross-linking the material. This avoids damage to an otherwise already rigid cage during the insertion of the rotating bodies.

Description: The invention relates to a method of manufacturing a rolling element bearing, which rolling element bearing is provided with rolling elements and a cage, whereby the cage over its annular circumference comprises receiving means for the rolling elements, is formed from cross-linked thermoplastic polymer-containing material, is provided with rolling elements, and is assembled into a rolling element bearing. Such a method is known from DE-A-4 041 068. This publication discloses a method of manufacturing a bearing provided with a plastic cage comprising a cross-linked polyphenylene sulphide resin. The plastic is sufficiently flexible to allow the incorporation of rolling elements. The cages manufactured according to this method have the disadvantage that under a heavy load the cage looses its rigidity, form and functionality. This may cause damage or destruction of the rolling element bearing and may in some applications lead to dangerous situations. Moreover the polymer-containing material used is relatively expensive. The present invention aims at improving a method of the manufacture of bearings comprising cages from cross-linked polymer-containing material, whereby the above-mentioned problems are effectively eliminated. To this end the method according to the invention is characterized in that first a cage is formed from cross-linkable, thermoplastic polymer-containing material, that it is then provided with rolling elements and that the material is subsequently cross-linked under the influence of radiation and the cross-linked material-containing cage. This method is particularly useful when applying a cage having receiving means for rolling elements whereby the openings of the receiving means is smaller than the diameter of the rolling elements. The cage of which the material is not yet cross-linked and which is still somewhat flexible can, because of its flexibility be provided with rolling elements without being damaged, which is good for the operational life and allows operation under heavy loads. The radiation is preferably ionizing radiation, especially β-radiation. In this way the intended cross-linking is effectively brought about. β-radiation possesses sufficient penetration and is radiation technically easy to handle. The invention will be further elucidated with the aid of the drawing which shows an example of an embodiment of a cage for a rolling element bearing manufactured according to the invention and in which the only Figure shows a radial view of the cage for a rolling element bearing. The figure shows part of a cage 1 which over its circumference is provided with receiving means 2. The cage is formed from a material containing a thermoplastic synthetic material which is subsequently cross-linked. The synthetic material may be one of the common nylons or polyether ether ketones. However, the invention allows the use of a great variety of cheap plastics such as polypropylene, mixed polypropylenes and polyurethanes. The receiving means 2 shown here have an opening 3 which is smaller than the diameter of the rolling elements A to be placed into the receiving means 2, so that the rolling elements A are retained in the receiving means. The rolling elements A consist of balls, but can for instance also comprise rollers. According to a preferred embodiment the cage 1 is provided with the rolling elements A before the polymer-containing material is cross-linked. This prevents that a cage, which in order to function properly is rigid and as mentioned before is provided with receiving means 1 having openings 2 which are smaller than the diameter of the rolling elements A, incurs damages during insertion of the same, in the form of, for instance haircracks. In order to improve the flexibility the polymeric material can contain additives such as a plasticizer. The plasticizer is also cross-linked under the influence of radiation. The polymeric material can also be provided with additives that promote cross-linking. If the polymer that is used is difficult to cross-link, such as polyamide, the application of such additives is very advantageous. Examples of cross-linking promoters are easily cross-linkable polymers such as polyethylene. Applying cross-linking promoters can at the same time improve the efficiency of the radiation sources, so that radiation sources can be used which would otherwise be less suitable. The degree of cross-linking is adapted to the desired properties. A higher degree of cross-linking results in a less elastic and harder cage. To influence the properties of the cage, additives such as fibre, in particular glass fibre and carbon fibre, can be incorporated in the polymeric material.

Claims: A method of manufacturing a rolling element bearing, which rolling element bearing is provided with rolling elements and a cage, whereby the cage over its annular circumference comprises receiving means for the rolling elements , is formed from cross-linked thermoplastic polymer-containing material, is provided with rolling elements and is assembled into a rolling element bearing, characterized in that first a cage is formed from cross-linkable, thermoplastic polymer-containing material, that it is then provided with rolling elements and that the material is subsequently cross-linked under the influence of radiation resulting in the cross-linked material-containing cage. A method according to claim 1, characterized in that the radiation is ionizing radiation. A method according to claim 2, characterized in that the ionizing radiation is β-radiation.

Inventors: BERRYMAN LESLIE, BRAS JOHAN CHRISTIAN MARINUS, TADIC VENDRAN ANDELO, BERRYMAN, LESLIE, BRAS, JOHAN CHRISTIAN MARINUS, TADIC, VENDRAN ANDELO
Applicants: SKF IND TRADING & DEV, SKF INDUSTRIAL TRADING & DEVELOPMENT CO, B.V.
Application year: 1994
Main classification: F16C33
IPC codes: F16C33, B29C35, B29C71, F16C43